Dry eye disease is a condition where the tear film loses water and becomes more concentrated, which can cause a corresponding rise in tear osmolarity. This increased osmolarity can result in symptoms such as a sandy-gritty feeling in the eye, burning, irritation, or a foreign-body sensation. As set forth in US Patent Application No. 2003/0203849, dry eye patients have been increasing in recent years with spread of use of contact lenses and increase in a VDT-operation.
Also as reported in US Patent Application No. 2003/0203849, lacrimal fluid serves other functions in addition to prevention of dry eye, such as, protection of cornea and conjunctiva, bacteriostatic action, prevention of infection with bacteria, fungus, virus and the like, feeding of oxygen and a variety of nutritions to cornea and removal of a carbon dioxide gas and metabolites therefrom, dilution and removal of harmful stimuli in the case where cornea and conjunctiva injured, transportation of liquid components such as epidermal growth factors which participate in wound healing and the like and hematocyte components such as fibronectin and the like to the injured portion, retainment of cornea and a conjunctival epithelial cell, regulation of wound healing.
As set forth in U.S. Patent Application No. 2005/0025810, dry eye disease may result from a number of s the following factors: (i) the disease may be a natural part of the aging process, affecting 15%-20% of adults over age 40; (ii) the disease may result from pathological processes such as diseases of the lacrimal glands, mucus glands, and/or lipid producing glands, and may occur with cell infiltration or atrophy of the lacrimal gland (Sjögren's syndrome); and (iii) estrogen deficiency in postmenopausal women may result in dry eye disease.
The proteinase-activated receptor-2 (PAR-2) is a G-protein-coupled receptor that is activated by proteolytic cleavage of the amino terminus extracelular domain, which unmasks a tethered peptide ligand that auto activates the receptor. PAR-2 is activated by trypsin and mast cell tryptase (see, e.g., Nystedt, et al., Eur J. Biochem 232(1):84-89 (1995); Bohm, et al., Biochem J 314, 1009-1016 (1996); and Molino, et al., J. Biol Chem 272(7):4043-49(1997)), as well as by synthetic peptides corresponding to the first amino acids of the receptor's tethered ligand: SLIGKV-NH2 (human sequence) or SLIGRL-NH2 (“SLIGRL”; mouse and rat sequence which is actually more potent than the human sequence for PAR-2 activation).
PAR-2 is expressed in many tissues, including the human cornea and human corneal epithelial cell lines (see, R Lang et al, Invest Ophthalmol Vis Sci. 44(1):99-105 (2003)). PAR-2 activity has been associated with inflammatory reactions in many tissues (see, e.g., Steinhoff et al, J Neurosci. 16;23(15):6176-80 (2003), Seeliger, et al., FASEB J. 17(13):1871-85(2003), and Uehara, et al., J Immunol 170(11):5690-96 (2003)).
PAR-2 activation in corneal epithelial cells induce intracellular calcium rise followed by pro-inflammatory cytokines release (R Lang et al, Invest Ophthalmol Vis Sci. 44(1):99-105 (2003)). PAR-2 activation by SLIGRL was shown to induce Tear Secretion in Rats (Nishikawa H et al, J Pharmacol Exp Ther. 2005 January ;312(1):324-31). US Patent Application No. 2003/0203849 discloses the use of the peptide SLIGRL, which activates PAR-2, for promoting tear secretions.
Mucin1 is one of the mucins expressed in the ocular surface (see Gibson, Exp Eye Res. 78(3)379-88 (2004)). Since ocular surface drying diseases also alter mucin production, it is expected that studies of mucin gene regulation may yield treatment modalities for these diseases (see Gibson, Exp Eye Res. 78(3)379-88 (2004)).
Applicants have unexpectedly found that the peptide LIGR induces the expression of the mucin1 gene in corneal epithelial equivalents. Applicants have found that unlike SLIGRL, the peptide LIGR does not induce calcium mobilization, and does not induce the secretion of inflammatory mediators, so the peptide is not activating PAR-2 like SLIGRL. Moreover, since LIGR is not inducing the secretion of inflammatory mediators, the peptide could be more useful in the treatment of dry eye conditions.